|其他摘要||Begonia section Platycentrum (Klotzsch) A. DC. distribute only in Asia. Based on literature collection, specimens checking, field work, greenhouse investigation and previous research work, the taxonomy on group laminariae and group Palmata of Begonia section Platycentrum from China were studied and the main results are showed as follows.
1. The macromorphology of all species of these two groups in Begonia sect. Platycentrum (Klotzsch) A. DC from China were supplemently discribed and summarized.
2. Macromorphological observation showed high diversity exist in the morphological characters, especialy the shape of leaves of these two groups, which give birth to the presence of many easily confused allies. Even in a same species, the macromorphology of leaves show some difference with the change of habitual environment. Therefore, it’s hardly to define the boundary of species by only based on studies of single characters.
3. Leaf epidermal micromorphorlogy characters of 52 species and two varieties, representing seven sections of Begonia Linn. (Begoniaceaea) from China, were examined under light microscopy (LM). The high similarity of leaf epidermal micromorphology in the seven studied section determines that these characters are hard to be used in the distinguishing of sections. However, while limited in section Platycentrum, high diversity exist in these characters. The combination of them show obvious differentiation, providing their importance to define different allies in this section. With careful comparing, we found that the shapes of epidermal cells, the patterns of anticlinal wall, the types of ornament of epidermal cells, the types of calcium oxalate crystall and the types of stomatal apparatus have their significance on the distinguishing of eight allies in Begonia sect. Platycentrum (Klotzsch) A. DC., including group laminariae: (1) B. cucurbitifolia and B. tetralobata; (2) B. miranda and B. reflexisquamosa; (3) B. pedatifida and B. rubropunctata; group Palmata: (4) B. villifolia and B. purpureofolia. Meanwhile, the multiple leaf epidermal characters also provided useful information for identification among other allies in sect. Platycentrum (Klotzsch) A. DC. (B. daweishanensis and B. dryadis) and in other sections of Begonia from China, such as in B. sect. Coelocentrum [(1) B. crystallina and B. bonii; (2) B. fimbribracteata and B. masoniana] and B. sect. Diploclinium (Wight) A. DC. (B. cavaleriei, B. peltatifolia and B. wangii. In addition, calcium oxalate crystal and stomatal clusters were treated as possible important mechanism for ecoloical adaptation in Begonia Linn. based on literatures studies and field investigation.
4. The observation of progenitive organs found that great consistency in the character of these organs in species of this section , making them being siginificant futures to separate this section from others. These futures: two locules, placentation axillary and two placental branches per locule always keep steady, or sometimes the branches would divide once again in some species. Although the morphologies of locules were variable at species level, but it’s unclear if this future can be used in species identification for our sample number is still poor. Even though, it’s still useful to put attention to the morphologies of locules to enrich the information for the systematic studies of this section, and more such work should be conducted to get a conclusion if these futures are informative for the taxonomy of section Platycentrum.
5. The ecological characters of some species in group laminariae and group Palmata in their flowering period and fruiting period were also observed. All studied objects are perennial and monoecious. Except for B. cucurbitifolia, these two group show high similarity in their ecology of flowering and fruiting. Species in group laminariae bloom mainly from June to December and fructify from August to March in the next year, while the ones in group Palmata respectively from June to December and from July to December. Generally, male flowers is predominant than female flowers in magnitude, and usually bloom earlier than the female flower. While young, stamens and stigma are usually yellow green or yellowish green, but stamens change to yellow and stigma to fresh yellow golden yellow in mature. The stigma with pollination become atrophic and the capsules are hard to fall off while the one without tend to fall off easily. With the growth, maturation and drying of capsules, seeds release from the dry capsule from cracked abdominal suture or back suture. All of these indicate similarity between group laminariae and group Palmata in habit and Phenological characters. Based on studies of habit and Phenology of group laminariae and group Palmata, it is possible that the combination of flowering periods and alttitute is one of reasons for high diversity in Begonia sect. Platycentrum group laminariae and group Palmata.
6. Based on the literatures, field work , greehouse investigation, examination of the specimens in GXMI, HAST, IBK, IBSC, KUN, PE, YUKU, and leaf epidermal micromorphology study, group laminariae and group Palmata in Begonia sect. Platycentrum were revised. 25 species and 10 varieties are recognized from China. Morphological characters and distribution trait of all these species and varieties are described and a key for the identification of them is given.
(1) Begonia sect. Platycentrum should be divided into two series: ser. Laminariae R. M. Zhang and ser. Palmata R. M. Zhang.
(2) Begonia miranda Irmsch. should not be included in Begonia sect. Diploclinium (Wight) A. DC. but in Begonia sect. Platycentrum (Klotzsch) A. DC. (Ku et al., 1999).
(3) Begonia reflexisquamosa should be a distinct species, not the synonym of Begonia miranda Irmsch.(Huang et Shui, 2006)
(4) Begonia purpureofolia S. H. Huang et Y. M. Shui should be treated as Begonia villifolia var. purpureofolia（S. H. Huang et Y. M. Shui）R. M. Zhang.
(5) The statuses of five names are uncertain.|